1. Field of the Invention
The present invention relates in general to a coil packing line for packing coils, such as coiled steel, and, more particularly, to a coil packing line in which coils are moved within the coil packing line using reciprocating carriages having a hoisting and lowering mechanism, thereby overcoming the problems in the conventional coil packing lines of the chain conveyor type, etc.
2. Description of the Related Art
Sheet metal products obtained by rolling are generally wound into metal coils (hereinafter simply referred to as "coils"), which are packed in packing material for shipment.
The coil packing line for packing these coils uses a chain conveyor or a walking beam as the equipment for conveying the packed coils, all the coils in the line being conveyed simultaneously at a fixed pitch (distance from one another).
Japanese Utility Model Laid-Open No. 56-162217 discloses conventional chain conveyor type coil conveying equipment, which equipment is shown in FIGS. 8 and 9. In this conventional equipment, a number of saddles 51, which are arranged at a fixed pitch, are conveyed by a chain conveyor 50, with each saddle supporting a coil W to be conveyed.
However, such a conventional coil packing line using a chain conveyor or a walking beam, which simultaneously conveys a number of coils at a fixed pitch, has the following problems.
Firstly, due to the large installation space for the packing line, a large floor space is required. Also, the return side of the line is below the surface of the floor, so that a deep foundation is required, resulting in a high foundation construction cost.
Secondly, the conveyance of coils cannot be started until the packing processes for all the coils in the packing line have been completed, so that the expensive automatic packing machinery provided in the line works at a rather poor rate of operation, i.e., spends more time than optimal in a non-operational state.
Thirdly, due to structural limitations, the distance between adjacent coils being conveyed is fixed. Therefore, even if the optimum distance between adjacent stages (and thus adjacent coils) is known, it is necessary in reality to choose a distance which is approximately an integral multiple of the various optimum distances (conveyance pitches) and which is larger than that optimum distance between any two adjacent stages. Thus, the length of the entire packing line becomes excessively large, resulting in a high construction cost.
To solve the above problems, Japanese Patent Laid-Open No. 2-286510 proposes an apparatus in which the conveyance between the processing stages is performed by carriage-type conveyors.
In the apparatus disclosed in the above-mentioned publication, a plurality of carriages are linked together and are moved simultaneously. The forward and return passages of the packing line are connected by a traverser. That is, each carriage is conveyed from the end of the forward passage by the traverser to the return passage. The return passage is linked to the forward passage, and thus the carriages circulate through the system.
The above-described conventional apparatus of Japanese Patent Laid-Open No. 2-286510 has a problem in that the traverser equipment connecting the forward and return passages is provided separately from the return passage, resulting in a high equipment cost. Further, the above-discussed second and third problems are still present.